French investigators have found that an Air Algerie Boeing 737-800, registration 7T-VJM on a commercial flight AH-1086 from Tlemcen (Algeria) to Paris Orly (France) on 6 December, 2019 experienced the startle effect linked to a go-around ordered by the Air Traffic controller which prompted the aircraft to lose altitude while the aircraft crew was attempting to climb.
As the aircraft was on approach to Orly’s runway 25, a vehicle went past the hold short line on taxiway W33 and came to stop at the runway edge.
Tower received a RIMCAS alert and instructed the aircraft to go around. The aircraft, already past the runway threshold, initiated a go around from very low height, climbed to 2000 feet on runway heading, then turned left and lost height descending to 1250 feet AGL before climbing again to 3000 feet MSL.
The aircraft positioned for another approach and landed safely on runway 25 about 25 minutes after the go around. BEA in their final report on October 12th 2021 concluded that the incident was serious.
The controller’s messages to warn the crew of the plane’s descent, along with the GPWS warnings, probably contributed to the crew realising that they were on an erroneous path and to them levelling off the plane.
The French investigation authority, BEA reported the first officer (CPL, 3,700 hours total, 1,700 hours on type) was the pilot flying, the captain (ATPL, 8,000 hours total, 1,400 hours on type) was pilot monitoring.
The crew performed an ILS approach to Orly’s runway 25 and was cleared to land on runway 25. Descending through 600 feet autopilot and autothrust were disengaged to perform a manual landing about 2 minutes after receiving landing clearance.
When the aircraft descended through 477 feet MSL (13 feet below the DA) the controller instructed the crew to go around. The controller did not inform the crew about the reason for this instruction – the RIMCAS alert for the runway had activated.
At 401 feet MSL (117 feet AGL ) the crew activated TOGA and set a nose up attitude. As autothrottle was disengaged and had not been armed, the engines did not spool up, the crew advanced the power levers to a position corresponding to about 90% N1.
The aircraft started to climb again after reaching a minimum height of 73 feet. The vertical climbing speed increased to about 4000 fpm. The aircraft was assumed to climb to 2000 feet MSL. Climbing through 380 feet the crew reduced the flaps to 15 degrees and retracted the landing gear.
Autothrottle was armed and as the flight director began to acquire the target altitude of 2000 feet autothrottle activated itself at 1340 feet MSL and engaged in SPD mode to maintain 171 KIAS.
With the autopilot still disengaged and the first officer’s input following the flight director indications the aircraft levelled off reaching a maximum of 2070 feet MSL, the engines spooled down and the IAS reduced to 160 knots, the aircraft was in a left turn reaching 38 degrees of bank angle, a ‘bank angle’ warning sounded.
The pitch remained at 4 degrees despite the F/D commanding 10 degrees nose up, the aircraft rolled out at about 200 degrees heading at 1900 feet MSL descending at more than 1500 fpm.
At that point ATC instructed the crew to climb to 3000 feet and turn to 160 degrees, the new target altitude was selected into the Master Control Panel (MCP), which resulted in the F/D transition from ALT ACQ mode into V/S hold mode (maintaining the current vertical speed), which was 1100 fpm descent at that point.
The engines slowed through 45% N1 and the pitch inputs followed the F/D indications still maintaining about 1100 fpm descent. The crew read back the clearance to maintain 3000 feet at the controllers request, disengaged the A/T and progressively increased thrust to about 50% N1.
A GPWS “Don’t Sink!” aural alert activated at 1,556 feet MSL at 1200 fpm descent. The crew activated A/T again with a MCP Speed of 175 KIAS, a few seconds later the controller informed the crew he was seeing them descend and instructed them again to climb to 3000 feet.
At an altitude of about 1300 feet MSL the crew fully retracted the flaps, disengaged A/T and progressively increased thrust to about 70% N1 and increased the pitch to 11 degrees nose up. The stick shaker briefly activated, the pitch was reduced, the F/D still commanded a pitch attitude consistent with a 1100 fpm descent.
The “DON’T SINK” GPWS alert again sounded. In the next 30 seconds the crew maintained 1300 feet MSL with the airspeed increasing to 292 KIAS, the crew extended the first stage of flaps exceeding the maximum flap speed by 20 KIAS then retracted them again, the autothrottle was engaged and the aircraft climbed to 3000 feet at 4000 fpm climb rate.
The F/D command bar still indicated a descent until the ALT ACQ mode activated. The crew engaged the autopilot again. Without further incidents the aircraft positioned for another approach to runway 25 and landed safely.
The BEA analysed with respect to the RIMCAS alert:
The RIMCAS warning was triggered by the presence of a bird-control vehicle at holding point W33 (north of the runway at around 700 m from the threshold). The crew of 7T-VJM had just been cleared to land when the LOC assistant controller, over the dedicated frequency, asked the driver of this vehicle to exit the runway safety area, but the driver did not reply. The LOC controller then asked the crew to perform a go-around.
The driver indicated that he had not heard the radio message as he was in the process of scaring off birds using gun fire. Furthermore, he had ensured that he was not in the runway safety area.
The air navigation services indicated that the RIMCAS warning was generated due to an erroneous system configuration. On completion of the work carried out up to 2 December on runway 25, four days before the event, the position of holding point W33 had been modified and moved 12 m closer to the runway centreline.
The RIMCAS configuration, which took into account the position of the holding points, had not been modified accordingly. The warning was therefore activated when the bird-control vehicle had not exceeded the holding point.
The RIMCAS configuration was corrected after the incident and the RIMCAS monitoring surface now corresponds to a 90 m rectangle on both sides of the runway centreline and separate from the position of the holding marks, in accordance with the runway 25 safety area.
The BEA further analysed:
In the scope of the investigation into the incident to the Airbus A350 registered F-HREV operated by French Bee that occurred on the 4 February 2020 at Orly, the BEA was able to determine, with the help of the Orly air navigation services, that out of the eight go-arounds at Paris-Orly in 2019 giving rise to a deviation of more than 200 ft with respect to the cleared altitude, six had a stabilization altitude at 2,000 ft. However, the go-arounds with a cleared altitude at 2,000 ft only represent 21% of all the go-arounds in the same period.
At the end of the investigation into the incident to F-HREV, the BEA recommended to the DSNA (the French air navigation service provider) that it study the feasibility of increasing the published missed approach altitude at Paris-Orly airport to give crews more time to carry out all the tasks associated with a go-around procedure and limit the risk of a path deviation.
The BEA also analysed:
During the simulations carried out in the scope of the study, it was noticed that the crew’s reading of the FMA was often deficient during the go-around.
Up to ten undetected FMA mode changes were observed during the same go-around, although some of these had a direct consequence on the tracking of the flight path. The nondetection of FMA mode changes by the two crew members is principally linked to cognitive saturation, time pressure, the absence of a defined visual scan pattern and the workload associated with a missed approach.
Likewise, on intercepting or selecting the go-around altitude, simulations showed that mode reversions were sometimes not detected.
Based on these observations, the BEA issued the following recommendation:
“EASA(14), in coordination with the major non-European certification authorities, ensure that aircraft manufacturers modify ergonomics so as to simplify the interpretation of FMA modes, and facilitate detection of any changes to them; [Recommendation FRAN-2013-037].”